Incineration ashes produced when general wastes and industrial wastes are incinerated below 900° C. contain toxic substances such as PCB, dioxins, lead and cadmium. Among other means to process such toxic substances, incinerators that operate using common fuels are incapable of processing these toxic substances.
As a means to process incineration ashes, a technique using an electric resistance furnace for melt-processing has been proposed. In particular, JP 2002-254052A discloses one such technique for melt-processing incineration ash. In this technique, a gas drawn out from within a hermetic electric resistance melting furnace is subjected to a dust collection process. The processed gas is circulated back into the melting furnace. While the dust collection process of the furnace gas is repeated, incineration ashes are charged into the melting furnace where they are melted. The resulting exhaust gas discharged from the melting furnace is then introduced into an exhaust gas-processing unit.
Thermal plasma is used as a means to process general industrial wastes, such as melt-processing of incineration ashes. Use of thermal plasma can insolubilize incineration ashes discharged from garbage incinerators and heavy metals present in the incineration ashes and can decompose dioxins to make them harmless. In 1994, an experimental furnace was installed in Matsuyama in a plant for melt-processing incineration ashes using thermal plasma.